1. Field
Exemplary embodiments consistent with the present disclosure relate to an optical device, and more particularly, to a high speed optical shutter, a method of operating the high speed optical shutter, and an optical apparatus including the high speed optical shutter.
2. Description of the Related Art
An optical shutter for transmitting or blocking an optical image according to a control signal is a main optical module that is widely used in photographing apparatuses including cameras, and a display device including a liquid crystal display (LCD) device.
Recently, research into three-dimensional (3D) cameras or laser radar (LADAR) technology for obtaining distance information of an object is being conducted. In this regard, 3D cameras and the LADAR technology measure a distance between a photographing apparatus and a subject by using time-of-flight (TOF) of light.
A shuttered light pulse (SLP) method from among various TOF methods involves emitting light of a particular wavelength to a subject, shuttering an optical image of the wavelength which is reflected from the subject, obtaining an image via an imaging device, performing a series of processes, and thus obtaining distance information. In order to distinguish between travel times of light according to distances, it is necessary for the SLP method to include a rapid shutter operation having an opening and closing conversion time of less than several nano-seconds (ns). For this, an image intensifier or a semiconductor-based optical shutter has been proposed as a high speed optical image shutter.
However, the image intensifier is an expensive piece of equipment demanding a high voltage and vacuum packaging. Also, although the semiconductor-based optical shutter may overcome disadvantages in operation and structure of the image intensifier, the semiconductor-based optical shutter is manufactured in a GaAs substrate via a semiconductor manufacturing process and has a complicated structure, compared to a photo-diode and a light emitting diode (LED) device used in the related art, and thus it may be relatively difficult to commercialize the semiconductor-based optical shutter with respect to price and manufacturing difficulty.
Meanwhile, an optical modulation device using an electro-optical effect according to the related art includes a Kerr cell or a Pockel cell. The optical modulation device using an electro-optical material has a response speed of several GHz, and thus has been used in waveguide in high speed optical communication.
In the optical modulation device, a polarization characteristic of a nonlinear crystal formed of lithium niobate (LiNbO3) or the like is changed according to a given electric field. That is, the optical modulation device has a shutter function so as to transmit or block a polarized incident light by controlling an angle of polarization by using an external electric field.